Heat-peelable pressure-sensitive adhesive sheets comprising a substrate and formed thereon a pressure-sensitive adhesive layer containing a foaming agent or expanding agent, e.g., heat-expandable microspheres, have conventionally been known (see, for example, JP-B-50-13878, JP-B-51-24534, JP-A-56-61468, JP-A-56-61469, and JP-A-60-252681; the terms “JP-B” and “JP-A” as used herein mean an “examined Japanese patent publication” and an “unexamined published Japanese patent application”, respectively). These heat-peelable pressure-sensitive adhesive sheets combine adhesiveness and peelability after use. This kind of pressure-sensitive adhesive sheet is characterized in that the adhesive force thereof is lowered by thermally foaming or expanding the foaming agent or expanding agent and, as a result, the adhesive sheet can be easily peeled from the adherend. Due to this characteristic, these pressure-sensitive adhesive sheets are used as a means for temporary fixation in the production of electronic parts and as labels to be recycled, etc.
With the recent trend toward capacity increase and size reduction in hard disks for use as a storage device in personal computers and the like, recording/reproducing magnetic heads of the type having a high areal recording density have come to be employed. At present, GMR (giant magnetoresistive) heads are coming to be mainly used. Although heat-peelable pressure-sensitive adhesive sheets are used for temporary fixation also in the production of such GMR heads, there has been the following problem. Since the GMR heads have poor resistance to static electricity, electrostatic breakage occurs due to static electricity generated in the head production process, resulting in an impaired yield of products.